RUI: Gas and Aerosol Phase Chemistry of Multi-Generation Isoprene Oxidation Products

RUI：多代异戊二烯氧化产物的气相和气溶胶相化学

• 批准号: 1153861
• 负责人: Matthew Elrod
• 金额: $ 35.51万
• 依托单位: Oberlin College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-15 至 2017-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1153861&HistoricalAwards=false
• 关键词: RUI; Gas; Aerosol; Phase; Chemistry

The atmospheric oxidation of volatile organic compounds (VOCs) influences the production of tropospheric ozone and secondary organic aerosol (SOA) with consequences for human health and global climate. Isoprene emitted by vegetation is the dominant VOC in many environments. However, both the ozone- and SOA-forming potential of isoprene remains uncertain. Modeled ozone production from isoprene is highly sensitive to the uncertain mechanistic representation of nitrogen oxides (NOx). In addition, "bottom-up" calculations based on isoprene emission data and chemical mechanisms underestimate SOA concentrations in isoprene-dominated environments. These gaps in understanding constrain the accuracy of air pollution and climate models. While the initial set of reactions that follow the OH radical attack on isoprene have been reasonably well characterized, the subsequent chemical processing of these first generation products (also known multi-generation steps) have received considerably less study and many of the key kinetics parameters that are required for quantitative prediction have not been characterized. This project will investigate the gas- and particulate-phase chemistry of the multi-generation isoprene oxidation products. Specifically, it will evaluate (a) the kinetics and products of the OH radical-initiated reactions of the organic nitrates formed as first-generation products of OH + isoprene, (b) kinetics and products of the OH radical-initiated reactions of dihydroxy-epoxides formed from OH + isoprene, (c) products of OH + methacrolein, including the H-atom abstraction/OH addition branching ratio, and (d) the esterification kinetics of 2-methylglyceric acid and 2-nitrato-2-methylglyceric acid (previously identified as components of isoprene-derived secondary organic aerosol), and of the reverse hydrolysis reaction. The gas-phase experiments will utilize the turbulent flow chemical ionization mass spectrometry technique, which allows OH and NOx levels to be controlled independently. The particulate-phase experiments will utilize bulk solution/NMR and aerosol chamber/aerosol scrubbing/NMR techniques.Results of this research effort will help improve current predictive capabilities for atmospheric chemistry and thereby facilitate informed public policy decisions regarding mitigation strategies for regional air pollution and climate change. This project will also contribute towards the development of the human resources necessary for the nation's scientific enterprise. The direct involvement of undergraduate students in original research will help prepare them for future careers in science as well as contribute to the increasingly interdisciplinary nature of the science experience at Oberlin College. The project will take place at an institution that is a national leader in the area of undergraduate science education and research and that has had an enduring commitment to increasing the number of underrepresented students in the sciences.

大气中挥发性有机化合物(VOCs)的氧化会影响对流层臭氧和二次有机气溶胶(SOA)的产生，从而对人类健康和全球气候造成影响。在许多环境中，植物排放的异戊二烯是主要的VOC。然而，异戊二烯的臭氧和SOA的形成潜力仍然不确定。模拟的异戊二烯臭氧产生对氮氧化物(NOx)的不确定机理表示高度敏感。此外，基于异戊二烯排放数据和化学机制的“自下而上”计算低估了异戊二烯占主导地位的环境中的SOA浓度。这些理解上的差距限制了空气污染和气候模型的准确性。虽然羟基自由基攻击异戊二烯后的最初一系列反应已经得到了很好的表征，但这些第一代产物的后续化学处理(也称为多生成步骤)得到的研究相当少，定量预测所需的许多关键动力学参数还没有得到表征。该项目将研究多代异戊二烯氧化产物的气相和颗粒相化学。具体地说，它将评估(A)作为羟基+异戊二烯第一代产物形成的有机硝酸盐的羟基引发反应的动力学和产物，(B)由羟基+异戊二烯形成的二羟基环氧化物的羟基引发反应的动力学和产物，(C)羟基+甲基丙烯醛的产物，包括氢原子抽提/羟基加成支化比，以及(D)2-甲基甘油酸和2-硝基-2-甲基甘油酸(以前被确定为异戊二烯衍生的二次有机气雾剂的成分)的酯化动力学，以及反向水解反应。气相实验将利用湍流化学电离质谱仪技术，允许单独控制OH和NOx水平。颗粒物阶段的实验将利用散装溶液/核磁共振和气雾室/气溶胶洗涤/核磁共振技术。这项研究的结果将有助于提高目前对大气化学的预测能力，从而促进关于区域空气污染和气候变化缓解战略的知情公共政策决策。该项目还将有助于开发国家科学事业所需的人力资源。本科生直接参与原创研究将有助于他们为未来的科学职业生涯做准备，并有助于奥伯林学院日益增长的跨学科性质的科学体验。该项目将在一个在本科科学教育和研究领域处于全国领先地位的机构进行，该机构一直致力于增加科学领域代表性不足的学生数量。